Added FileIO-like methods to BaseStorageFile

Author: gave92

Files/Extensions/ShellNewEntryExtensions.cs

@@ -85,12 +85,8 @@ public static async Task<FilesystemResult<BaseStorageFile>> Create(this ShellNew
             {
                 if (shellEntry.Data != null)
                 {
-                    //await FileIO.WriteBytesAsync(createdFile.Result, this.Data); // Calls unsupported OpenTransactedWriteAsync
-                    using (var fileStream = await createdFile.Result.OpenStreamForWriteAsync())
-                    {
-                        await fileStream.WriteAsync(shellEntry.Data, 0, shellEntry.Data.Length);
-                        await fileStream.FlushAsync();
-                    }
+                    //await FileIO.WriteBytesAsync(createdFile.Result, shellEntry.Data); // Calls unsupported OpenTransactedWriteAsync
+                    await createdFile.Result.WriteBytesAsync(shellEntry.Data);
                 }
             }
             return createdFile;

Files/Filesystem/StorageItems/BaseStorageItem.cs

@@ -3,6 +3,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Runtime.InteropServices.WindowsRuntime;
+using System.Text;
 using System.Threading.Tasks;
 using Windows.Foundation;
 using Windows.Foundation.Metadata;
@@ -461,5 +462,40 @@ StorageItemContentProperties IStorageItemProperties.Properties
                 return null;
             }
         }
+
+        public async Task<string> ReadTextAsync(int maxLength = -1)
+        {
+            using var inputStream = await OpenSequentialReadAsync();
+            using var dataReader = new DataReader(inputStream);
+            StringBuilder builder = new StringBuilder();
+            uint bytesRead, bytesToRead;
+            do
+            {
+                bytesToRead = maxLength < 0 ? 4096 : (uint)Math.Min(maxLength, 4096);
+                bytesRead = await dataReader.LoadAsync(bytesToRead);
+                builder.Append(dataReader.ReadString(bytesRead));
+            } while (bytesRead > 0);
+            return builder.ToString();
+        }
+
+        public async Task WriteTextAsync(string text)
+        {
+            using var stream = await OpenAsync(FileAccessMode.ReadWrite, StorageOpenOptions.AllowOnlyReaders);
+            using var outputStream = stream.GetOutputStreamAt(0);
+            using var dataWriter = new DataWriter(outputStream);
+            dataWriter.WriteString(text);
+            await dataWriter.StoreAsync();
+            await stream.FlushAsync();
+        }
+
+        public async Task WriteBytesAsync(byte[] dataBytes)
+        {
+            using var stream = await OpenAsync(FileAccessMode.ReadWrite, StorageOpenOptions.AllowOnlyReaders);
+            using var outputStream = stream.GetOutputStreamAt(0);
+            using var dataWriter = new DataWriter(outputStream);
+            dataWriter.WriteBytes(dataBytes);
+            await dataWriter.StoreAsync();
+            await stream.FlushAsync();
+        }
     }
 }

Files/Filesystem/StorageItems/StreamWithContentType.cs

@@ -120,7 +120,8 @@ public NonSeekableRandomAccessStream(Stream baseStream, ulong size)
 
         public IInputStream GetInputStreamAt(ulong position)
         {
-            throw new NotSupportedException();
+            Seek(position);
+            return this;
         }
 
         public IOutputStream GetOutputStreamAt(ulong position)

Files/ViewModels/Previews/BasePreviewModel.cs

@@ -153,18 +153,7 @@ public override Task<List<FileProperty>> LoadPreviewAndDetails()
 
         public static async Task<string> ReadFileAsText(BaseStorageFile file, int maxLength = 10 * 1024 * 1024)
         {
-            using (var stream = await file.OpenStreamForReadAsync())
-            {
-                var result = new StringBuilder();
-                var bytesRead = 0;
-                do
-                {
-                    var buffer = new byte[maxLength];
-                    bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length);
-                    result.Append(Encoding.UTF8.GetString(buffer, 0, bytesRead));
-                } while (bytesRead > 0 && result.Length <= maxLength);
-                return result.ToString();
-            }
+            return await file.ReadTextAsync(maxLength);
         }
     }
 }